Prior developments in this field will be generally illustrated by reference to the following patents:
______________________________________ Pat. No. Patentee Issue Date ______________________________________ 2,530,423 C. Carson 11/21/50 2,657,610 W.E. Carran, Jr. 11/03/53 4,425,499 R.A. Newton 01/10/84 3,779,454 J. Koren 12/18/73 2,832,539 J.D. Blakeley et al. 04/29/58 2,585,595 N.S. Spencer 02/12/52 2,530,047 N.F. Dewar 11/14/50 ______________________________________
For large-scale projects, computers may be used to design combinational logic circuits. It is simply not worth the effort, however, to use a computer to design a small-scale digital circuit--so the traditional method, namely, pencil and paper, is still used. Therefore, there is a need for a small, inexpensive mechanical aid for designing digital circuits which provides easier, faster and less error-prone solutions than does manual computation, much in the way logarithmic slide rules were used in the past to solve arithmetic problems.
While the patents listed above teach slide rule and slide rule-like mechanical devices directed to a number of problems, none attempt to address logic circuit design. Furthermore, there are a number of physical differences between the device of the present invention and those shown in the cited art. C. Carson's calculating board, U.S. Pat. No. 2,530,423, shows multiple slides and multiple viewing windows. Parts 39 and 49 of Carson somewhat resemble the display plates taught infra. However, parts 39 and 49 of Carson are located externally and do not contain indicia.